Controller

Abstract

A controller comprises a valve body having a valve element and a valve seat defining a fluid cannel openable and closable with a reciprocating upward and downward movement of a valve stem, a casing fixed to an upper portion of the valve body, an operating rod provided in an upper inside portion of the casing upwardly and downwardly movably, a drive device for moving the rod upward and downward, and a transmission device provided in a lower inside portion of the casing for transmitting a force acting on the rod to the valve stem. The transmission device comprises a first roller contact member in the form of a downwardly flaring frustoconical recessed portion open downward and formed on an underside of a large-diameter portion of the rod concentrically therewith, a second roller contact member provided at an upper end of the valve stem, a pair of roller support members arranged between the two contact members symmetrically with respect to the axis of the operating rod, a pair of rollable rollers each rotatably supported by the support member at an upper portion thereof and bearing on a tapered face of the first roller contact member, and a pair of push rollers each rotatably supported by the support member at a lower portion thereof and bearing on an upwardly facing roller support surface of the second roller contact member. Each of the support members is supported by the casing so as to be pivotally movable about an axis outwardly spaced from the axis of the rod by a greater distance than the axis of the corresponding push roller.

What is claimed is: 
     
       1. A controller comprising a valve body having a valve element and a valve seat defining therebetween a fluid channel openable and closable with a reciprocating upward and downward movement of a valve stem, a casing fixed to an upper portion of the valve body, an operating rod provided in an upper inside portion of the casing and being upwardly and downwardly movable and having a small-diameter portion and a large-diameter portion integral with a lower end thereof and being mutually spacedly disposed along the longitudinal axis of said operating rod, drive means for moving the operating rod upward and downward, and power transmission means provided in a lower inside portion of the casing for transmitting a force acting on the operating rod to the valve stem, the power transmission means comprising a first roller contact member having a downwardly flaring frustoconical recessed portion opening downward and provided on an underside of the large-diameter portion of the operating rod concentrically with the rod, a second roller contact member provided at the upper end of the valve stem, a pair of opposed roller support members arranged between the two roller contact members symmetrically with respect to the axis of the operating rod, a pair of rollable rollers each being rotatably supported by each of the roller support members at an upper portion thereof and bearing on a tapered face of the frustoconical recessed portion, and a pair of push rollers each being rotatably supported by each of the roller support members at a lower portion thereof and bearing on an upwardly facing roller support surface of the second roller contact member, each of the roller support members being pivotably supported with respect to the casing so as to be pivotally movable about an axis perpendicular to and laterally spaced from the axis of the operating rod a distance greater than the spacing from said operating rod axis to the rotational axis of the corresponding push roller and effective to vertically move said stem by lateral movement of said push rollers in response to an opposite lateral movement of said rollable rollers induced by engagement with said tapered face of said recessed portion, during upward and downward movement of said operating rod by said drive means. 
     
     
       2. A controller as defined in claim 1 wherein when a working fluid is used as the drive means, the inside of the casing is divided into two upper and lower chambers by the first roller contact member with a spring disposed in the upper chamber for biasing the operating rod downward, and the working fluid is admitted into the lower chamber to urge the operating rod upward against the spring bias.